1. Field of the Invention
The present invention relates to time-division switching networks for transmitting PCM (Pulse Coded Modulation) speech signals and, more particularly, to means and processes for propagating speech samples and space-division switching cross-point addresses through large size networks including, at least, one time-division switching stage and one space-division multistage switch.
2. Description of the Prior Art.
Such time-division switching networks are well known and may be parts of local or toll exchanges. They are designed for handling a great number of ingoing or outgoing time-division channels. Every time-division stage includes separate time-division groups, each group being respectively connected to a separate individual link of the space-division switch.
In a known manner, the purpose of the space-division switch is to extend network capacity over limits resulting from present pure time-division switching network technology, and utilization of a space-division switch together with ingoing and outgoing time-division groups makes it possible to attain very large size networks.
In high-traffic large size networks, the space-division switch advantageously comprises several cascaded stages. The resulting drawback is that speech sample transfer time, via the space-division switch, increases as the number of stages. Transferring a sample through the space-division switch during a single network elementary time becomes difficult, whereas it may be performed readily in networks having smaller capacity.
Furthermore, the various cross-points contributing to a sample propagation path must be addressed. Due to the large number of time-division channels connected to networks of this kind, memory capacity reserved in the network for cross-point addresses is particularly important.